Dental articulator.



D. M. SHAW.

I DENTAL ARTICULATOR. APPLICATION FILED APR. 15. 1914.

1,178,045. Patented Feb. 22,1916.

@NITED %TATE% PATENT QFFEQE,

DAVID MACKINTOSH SHAW, O1? ELTHAM, ENGLAND, ASSIGNOR TO DENTAL MANUFAC-TURING COMPANY LIMITED, OF LONDON, ENGLAND.

DENTAL EART IGULATOR.

Specification of Letters Patent.

Patented Feb. 22, 1916.

Application filediAprill5, 1914. Serial No. 831,977.

tham, in the county of Kent, England, have invented new and usefulImprovements in and Relating to Dental Articulators, of which thefollowing is a specification.

This-invention relates to improvements in dental articulators designedmore particularly so that that portion of the instrument representingthe human condyle is con structed to copy and carry out exactly thosecharacteristic translation movement-s of the natural condyle in avertical plane which. are known always to take place when the lower jawis opened or :shut upon the upper jaw. The exact reproduction of thisparticular movement is of practical importance because at least somedegree of opening or shutting (vertical) movement takes place in all andevery normal chewing movement, whether lateral, protrusive, orcombinations of these movements. It is known that during this opening orshutting movement of the lower jaw upon the upper jaw there is alwayssimultaneously a combined movement of translation and rotation in thelower jaw and condyles in such a way that when the movement of rotationabout the condyles takes place with uniform velocity, the simultaneousmovement of translation of the condyles themselves takes place with avariable velocity which is slow or small in the beginning, quicker inthe middle, and slower again at the end of the condyle path. Ittherefore follows that while this combined movement of the natural lowerjaw may be at any instant resolved into a move ment purely of rotationabout a single point or axis, the position of this axis (called inkinematics the instantaneous center) changes from instant to instantrelatively to any point fixed on the lower or the upper jaw, so that itcannot be represented by any fixed point.

In the older type of articulating frame or articulator with a purelypivotal and non sliding joint, the artificial teeth required for either(upper or lower) jaw could be adjusted and arranged against the teeth ofthe opposing jaw only in that static or stationary relationship of theshut teeth which dentists term occlusion, and so the correctness oftheir arrangement :for efficiency in natural chewing movements could notpossibly be tested with such simple hinge frames or articulators. Toremedy this anatomical 'articulators were devised, the dlstinguishingfeature of all of which is, that the joint which controls the movementofone jaw relative to the other imitates the :natural jaw joint in sofar as to allow, in

addition to the rotation or simple-hinge movement, a sliding movement oftranslation also. The :aim of inventors has been toprovide .a jointmechanism by which the general character of the separate or comb nedmovements of rotation and transla tion observed in the natural livingjaw is imitated as closely as possible; and also so that any particularvariation of the natural joint movement observed in an individualpatient can be copied and reproduced in the articulator, with the primeobject of insuring that artificial teeth arranged so as to oppose oneanother and act in a certain preclse and efficient manner duringmovements on thearticulator will be related and act in exactly the samemanner during chewing movements in the mouth of that particular patient.

According to my invention I provide a dental ,articulator with a condylepart so constructed that during the movement of the arm carrying thelower jaw .part with uniform angular velocity, about the condyle, thecondyle part moves in an ogee or S-shaped path with a velocity whichvaries in the natural manner from point to point of. the movement, themotion being governed by means of a cam surface, and guideways for thecondyle, so that the combined rotation and translation movements of thelower arm is not a movement of rotation about any fixed point as inother articulators, but takes place only about an instantaneous center,as in the natural jaw. It .is thereby further effected that during thevertical openingv and shutting movements the translation path of thecondyle part is not the arc of a circle as insome articulators hithertoconstructed, but is in a double curved, non-circular or ogee or S-shaped path as in the natural human condyle. And, just as in the naturalj aw, although the translation or sliding movement may take place byitself and without other movement whenever desired, it is impossible.for :any opemng or shutting (vertlcal) movement to take place without asimultaneous movement of translation. Means are provided whereby thecondyle path can be varied and adapted to agree with the ascertainedpath ofany patient. I may also provide a mounting platform supported insuch a position on the articulating apparatus that its surfacerepresents the horizontal level and average relative position of theocclusal plane to the joint mechanism.

My invention is illustrated by way of example in the accompanyingdrawings, in which- Figure 1 shows a perspective view of my apparatuswith a set of anatomical teeth set up in position. Fig. 2 shows a detailview of the cam construction for producing the correct natural motion ofthe condyle path in opening and shutting movements. Fig. 3 shows adetailview of a cam construction representing the longitudinal jaws inposition of extreme opening. Fig. 4 shows a section on the line ab of Fig. 2, looking in the direction of the arrow. Fig. 5 shows a detailunderside plan View of the upper arm of the articulator and the springadapted to retain the cam surfaces on the lower arm against the engagingpins on the upper arm. Fig. 6 shows a perspective View of thearticulating apparatus with the mounting platform in position, and Fig.7

shows a detail view of an ogee or S-cam condyle member and its pivot.

Referring now to the drawingsI pro vide on the upper arm of thearticulator condyles in the form of ogee or S-cam shaped members 11,that means a cam surface composed of a concave and a convex curve. Thesaid ogee or S-cam shaped members 11 are mounted upon pivots providedwith locking pins 4 so that the posltion of said cam members can beadjusted and held rigidly in the position in which they are set to suitthe condyle path of any patient. The said members 11 are respectivelyadapted to engage between the guiding pins 12 projecting from the disk13 mounted on the lower arm of the articulator on pivots 14. In orderthat the disks 13 may be retained in position in a convenient manner, aset screw 15 is arranged to screw into each of their pivots 14, as shownin Fig. 4. The pins 7 on the upper arm engage respectively with thecurved cam surfaces 2 on the lower arm. The condyle movement is effectedby the said pair of pins 7, which pins are held in sliding contact withthe said corresponding curved cam surface 2. The pins 17 act as limitingstops in the extreme position of the articulator.

The cam surfaces 2 on the lower arm of the articulator are normallyretained in engagement with the pins 7 on the upper arm of thearticulator by means of the leaf spring 8 on said upper arm (shown indetail in Fig. 5) doubled over upon itself, so that its free end 9engages against the central portion of the cross bar 10 on the lower armof the articulator arranged inside and between the condyle joints. Thefront portion of the upper jaw member has an arm 16 directed verticallydownward, the extremity of which rests, when the jaw members are in theclosed position, upon the cam-shaped base 17 In combination with thearticulating apparatus I may provide a mounting platform 6 as shown inFig. 6 supported in such a position on the articulating apparatus thatits surface represents the horizontal level and average relativeposition of the occlusal plane. -The said platform is employed only forthose cases wherein it is not proposed to ascertain by individualmeasurements the exact position of the plaster jaws and occlusal planerelative to the joint.

In use the upper bite-plate with attached plaster model is placed flatupon it, the median line coinciding with the line scored upon theplatform and the incisal point coming just to its front edge. Nomeasurements are required. The said bite-plate 'may be held in positionwith a little wax or clay while the upper arm is being securelyplastered down upon the cast.

The claims in the present application are specific to the constructionof the articulator shown and described herein and the generic claims arefound in my copending application Serial No. 18,661 filedSeptember2,1915.

WVhat I claim is 1. In a dental articulator, the combina tion of anupper jaw member, a lower jaw member, ogee-cam condyle members-0n saidupper jaw member, pairs of guiding pins on said lower jaw memberrespectively adapted to receive said condyle members, controlling pinson said upper jaw member and cam surfaces on said lower jaw memberadapted to be engaged by said controlling pins and giving said condylemembers a variable velocity in their guideways during the movement ofthe pin members.

2. In a dental articulator, the combination of an upper jaw member, alower jaw member, pivots in said upper jaw member, condyle membersmounted on said pivots and each provided with double curved cam surface,locking pins adapted to hold the pivots of said condyle members at theangle in which they are set, pairs of guiding pins on said aw membersrespectively adapted to receive said condyle members, controlling pinson said upper jaw member and cam surfaces on said lower jaw memberengaged by 'said controlling pins and giving said condyle members avariable velocity in their guides during the movement of the jaws.

3. In a dental articulator, the combination of an upper jaw member, alower jaw member, condyles connecting said jaw members adapted to bemoved in ogee-shaped paths during the opening or shutting movements ofsaid jaw members, controlling pins on said upper jaw members, cammembers on said lower jaw member engaged by said controlling pins andgiving said condyles a variable velocity in their ogee-shaped paths, anda mounting platform supported on said lower jaw member in such aposition that its surface represents the horizontal level and averagerelative position of the occlusal plane.

4. In a dental articulator, the combination of an upper jaw member, alower jaw member, pivots in said upper jaw member, ogee-cam condylemembers mounted on said pivots, locking pins adapted to hold the pivotsof said condyle members at the angle Copies of this patent may beobtained for five cents each, by addressing the in which they are set,pairs of guiding pins on said lower jaw member respectively adapted toreceive said condyle members, controlling pins on said upper jaw member,cam surfaces on said lower jaw member adapted to be engaged by saidcontrolling pins and giving said condyle pins a variable velocity intheir guides during the movement of the jaws, and a mounting platformsupported on said lower jaw'member in such a position that its surfacerepresents the horizontal level and average relative position of theocclusal plane.

In testimony whereof I have signed my name to the specification in thepresence of two subscribing witnesses.

DAVID MACKINTOSH SHAW. Witnesses LEONARD E. HAYNES, CHARLES F OYER.

Commissioner of Patents,

Washington. D. C.

